The ATP World Tour Finals 2009 is a tennis tournament that took place from November 22nd to 29th at the O2 Arena in London . It was the 40th edition of the competition in singles and 34th in doubles. In addition to the four Grand Slam tournaments , the World Tour Finals are the most important competition in men's professional tennis; they take place at the end of the tennis year. World number six Andy Roddick did not take part in the competition due to an injury and was replaced by Robin Söderling .